Optical displays typically have an exposed viewing surface made from a thermoplastic film or slab. Commonly employed thermoplastic polymers have very good optical transparency, dimensional stability and impact resistance, but unfortunately have poor abrasion resistance. The optical displays of devices such as personal digital assistants (“PDAs”), cell phones, liquid crystal display (LCD) panels, touch-sensitive screens and removable computer filters are subjected to frequent handling and contact with the user's face or fingers, styli, jewelry and other objects. For example, facial oils can adversely affect contrast, color saturation or brightness of a cell phone display. The screens of projection televisions and laptop computers are handled less frequently but nonetheless are susceptible to being touched, scratched or smudged. Consequently, the viewing face of the display is susceptible to scratches, abrasion and smudges arising during routine use. This can cause the display to lose resolution and clarity, and sometimes to become unreadable or inoperative. To protect such displays, protective films or coatings can be employed.
Hardcoats have also been used to protect the face of optical displays. These hardcoats typically contain inorganic oxide particles, e.g., silica, of nanometer dimensions dispersed in a binder precursor resin matrix, and sometimes are referred to as “ceramers”.
U.S. Pat. Nos. 6,132,861 (Kang et al. '861); 6,238,798 B1 (Kang et al. '798); 6,245,833 B1 (Kang et al. '833); 6,299,799 (Craig et al.) and Published PCT Application No. WO 99/57185 (Huang et al.) describes ceramer compositions containing blends of colloidal inorganic oxide particles, a curable binder precursor and certain fluorochemical compounds. These compositions are described as providing stain and abrasion resistant hardcoats in a single layer coating.
U.S. Pat. No. 6,660,389 (Liu et al.) describes information display protectors for display devices having an information display area, comprising a stack of flexible substantially transparent sheets, the sheets having on one side thereof an adhesive layer and having on the other side thereof a hardcoat layer comprising inorganic oxide particles dispersed in a binder matrix and a low surface energy fluorinated compound, the stack being cut so that the sheets will fit the information display area. The low surface energy fluorinated compound can be part of the hardcoat layer or can be a separate layer atop the hardcoat layer. The protectors have very good scratch, smudge and glare resistance. The stack of protectors can be stored, for example, on a personal digital assistant or its cover or case.
JP 2000-301053 describes a hardcoat sheet and its production. The composition is composed of an alkyl fluoroacrylate A, an acrylic monomer B incompatible with A and containing at least 10% of an acrylic monomer having greater than or equal to three functional groups, an acrylic monomer C incompatible with A and containing at least 50% hydrophilic acrylic monomer and a solvent D compatible respectively with A, B and C.
WO 2004/002734 describes an object having a hard coating excellent in antifouling properties, lubricity, marring resistance, and wearing resistance; and a method of forming a hard coating. A hard coating material composition containing an actinic-energy-ray-curable compound is applied to a surface of an object (1) to be coated with a hard coating layer to thereby form a layer of the hard coating material composition. A film of a surface material comprising a fluorinated polyfunctional (meth)acrylate compound and a fluorinated monofunctional (meth)acrylate compound is formed on the layer of the hard coating material composition to form a layer of the surface material. The layer of the hard coating material composition and the surface material layer thus formed are irradiated with actinic energy rays to simultaneously cure both layers. Thus, a hard coating layer (2) in contact with the surface of the object (1) and an antifouling surface layer (3) in contact with the surface of the hard coating layer (2) are formed.
Although various surface coatings for optical displays have been described, industry would find advantage in new compositions that impart a synergistic combination of surface properties.